H. E. Kaufman, M.D. and others have identified a serious problem in intraocular lens implantation dealing with the destruction of corneal endothelium cells. It is generally recognized that the corneal endothelium will not regenerate itself and is extremely important as a boundary layer between the outer layers of the cornea and the aqueous humor in the anterior chamber of the eye. The corneal endothelium is extremely delicate in that the endothelium is only one cell thick.
The intraocular lenses commonly implanted are of a polymethylmethacrylate (PMMA) material which has excellent optical qualities and biocompatibility once it is surgically implanted. Once implanted the location of the intraocular lens is such that, when in its proper position, it does not contact or damage the corneal endothelium. There is a continuous washing or flushing of the anterior chamber including the corneal endothelium.
During surgical implantation of an intraocular lens, the cornea is surgically opened and the intraocular lens manipulated in place frequently with retention loops placed behind the iris. Sometimes the manipulation includes puncturing the iris with a miniature safety pin type prong or clip to attach the lens to the iris.
During the surgical implantation and manipulation, it frequently happens that the corneal endothelium is staticly touched or dynamically scraped with a PMMA lens or surgical tool. Dr. Kaufman and others have recognized the problem of corneal endothelium damage during surgery and have proposed dipping the lens in a coating of methylcellulose (MC) or polyvinylpyrrolidone (PVP). These coatings were applied by the ophthalmologist immediately prior to surgery as a wet and slippery coating on the lenses.
Dipping of the lenses in MC or PVP is useful to protect the corneal endothelium. However, because of a fast dissolution rate of these polymers and the difficulty of placing a controlled amount of such polymers on the lenses, the extent and length of the protection is uncontrollable. Because of the wet and slippery nature of the lenses dipped during surgery, the lenses are difficult to handle and a portion of the coating may drip off. In addition, MC and PVP solutions must be sterilized prior to dipping. Subsequently, Dr. Fechner (citation below) published the results of a repeat of the Dr. Kaufman et al experiments with a complicated attempt to sterilize methylcellulose in very small quantities to keep it from coalescing and changing viscosity. In practice, the complicated procedure described for the sterile methylcellulose coating is not feasible for the ophthalmologist to perform in the operating room.
The background publications by Dr. Kaufman et al explaining the corneal endothelium damage during intraocular lens implantation and experiments with methylcellulose and polyvinylpyrrolidone coating are as follows.
Kaufman, H. E. and J. I. Katz, "Endothelial Damage From Intraocular Lens Insertion," Inv. Ophth., Vol. 15(12), Dec. 1976, p. 996-1000 PA1 Kaufman, H. E., Jeffry Katz, et al, "Prevention of Endothelial Damage From Intraocular Lens Insertion," Tr. Am. Acad. Ophth. & Otol., Vol. 83, Mar-Apr. 1977, p. 204-212 PA1 Kaufman, H. E. and J. I. Katz, "Pathology of the Corneal Endothelium," Inv. Ophth. Visual Sci., Vol. 16(4), April 1977, p. 265-268 PA1 Fechner, P. U., "Methylcellulose In Lens Implantation," Jour. Amer. Intraocular Implant Society, Vol. 3(3 & 4), July-October 1977, p. 180-181 PA1 Kaufman, H. E., Jeffrey Katz, et al, "Corneal Endothelium Damage with Intraocular Lenses: Contact Adhesion Between Surgical Materials and Tissue," Science, Vol. 198(4316), Nov. 4, 1977, p. 525-527.